Method for discharging waste gas from submarines without a signature

ABSTRACT

The invention relates to a method and a device for discharging signature free exhaust gas from underwater vehicles, said exhaust gas being a by-product of the production of electric energy in energy converters and being directed by means of pressure into a pipe length through which outboard water is flowing. The thereby generated gas bubbles are reduced by means of static mixers arranged inside of the pipe length through which water is flowing, with the gas being dissolved by the high turbulence of the fluid.  
     As the exhaust gas is dissolved inside of the underwater vehicle, no gas bubbles that might be located are produced outside the vehicle. Since the working pressure of the method equals the immersion pressure, but little energy is consumed.

[0001] The invention relates to a method and a device for discharging signature free exhaust gas from underwater vehicles, said exhaust gas being a by-product of the production of electric energy in energy converters, and to such an underwater vehicle. When using hydrocarbons for delivering energy, energy converters, which serve to produce electricity in underwater vehicles without having to rely on outside air, not only produce electricity but also exhaust gas. Said exhaust gas must be stored on board or discharged from the vehicle. The solutions heretofore proposed are water management systems, the liquefaction of the exhaust gas and subsequent storage thereof or the direct discharge in the form of gas.

[0002] The document EP 0 752 565 B1 for example discloses an apparatus for the disposal of CO₂ in underwater vehicles. To dispose of the CO₂ in underwater vehicles, pressurized water has to be ingested from the outside into the underwater vehicle where it dissolves CO₂ with the assistance of an absorber after which this water, containing the dissolved CO₂, is to be redirected out of the vessel against the immersion pressure.

[0003] According thereto, there is provided an apparatus that has a housing which is provided with a circular internal tread for a rotating cam body, said internal tread being disrupted by opposite pairs of water inlet ports and water outlet ports, each water inlet port being separated from the water outlet port by a vane that is radially slidable on the cam body and a respective one of the inlet ports for high-pressure water alternating with an outlet port for low-pressure water and a respective one of the inlet port for low-pressure water alternating with an outlet port for high-pressure water on the circular internal tread of the housing. This apparatus is characterized in that it is provided with but a few movable parts and sealing surfaces and that it permits, with low internal flow resistance and without flow reversal, harmonious flow of the water transported for the disposal of CO₂, with the water bearing parts of the apparatus being treated with care and subjected to little strain as a result thereof.

[0004] In Schiff & Hafen/Seewirtschaft (Ship and Harbour/Sea Trade), Part 7/1992, pp. 43-46, the contribution “Der Kreislaufdiesel als auβenluftunabhängiger Antrieb für U-Boote” (Recirculation diesel as an air independent drive for submarines) describes a water management system that is suited to take in sea water for the absorbers and to release it again out of the vehicle.This water management system uses the energy of the sea water subjected to immersion pressure. The arrangement consists of control valves and of freely movable pistons that allow the diesel recirculation system to operate independent of the immersion depth. The feed pumps for the intake of sea water only need to compensate the resistances of the pipelines and of the fittings.

[0005] These systems require either lots of space or lots of energy or they result in signatures that make it easy to locate the underwater vehicle.

[0006] It is therefore the object of the present invention to discharge exhaust gas with low signature from the vehicle while requiring little space and energy.

[0007] In accordance with the invention, the solution of this object is achieved by the features of the claims 1 and 7. Advantageous developments of the invention are characterized in the depending claims 2 through 6 and 8 through 10 respectively.

[0008] Accordingly, the invention includes a method for discharging signature free exhaust gas from underwater vehicles, said exhaust gas being a by-product of the production of electric energy in energy converters and being directed by means of pressure into a pipe length through which outboard water is flowing. The thereby generated gas bubbles are reduced by means of static mixers arranged inside of the pipe length through which water is flowing, with the gas being dissolved by the high turbulence of the fluid.

[0009] As the exhaust gas is dissolved inside of the underwater vehicle, no gas bubbles that might be located are produced outside the vehicle. Since the working pressure of the method equals the immersion pressure, but little energy is consumed.

[0010] According to a preferred feature of the invention, the exhaust gas is introduced into the pipe length by way of a porous body, the exhaust gas being introduced into the pipe length at a pressure that preferably is above the immersion pressure. The pipe length is thereby supplied with outboard water (sea water) by way of a pump. According to a particular feature, the pipe length is supplied with outboard water (sea water) by the moving underwater vehicle, the outboard water being subjected to immersion pressure between the inlet and the outlet point. According to another feature, the flow velocity of the water inside the pipe length preferably amounts to 1-3 m/s.

[0011] The invention also comprises a device for discharging signature free exhaust gas from underwater vehicles, said exhaust gas being a by-product of the production of electric energy in energy converters. For the purpose thereof, at least one pipe length is arranged in the underwater vehicle, said pipe length being provided with an inlet for outboard water (sea water), an outlet for the exhaust dissolved in the water, and an injection site for the exhaust gas to be introduced into the pipe length. At least one static mixer is provided inside of said pipe length. According to another feature, a pump is arranged in the region of the inlet port for the outboard water of the pipe length. In accordance with another feature of the invention, the injection site consists of a quadrant pipe with an injection lance and a porous body. According to a preferred feature of the invention, the length of the pipe is such that it allows complete dissolution of the gas bubbles of the exhaust.

[0012] The invention will be described more explicitly in the following with the help of an embodiment illustrating an example and represented in the Figs in which:

[0013]FIG. 1 illustrates air independent energy supply,

[0014]FIG. 2 illustrates the device for discharging the exhaust gas.

[0015] In an energy converter system III for producing electric energy in an underwater vehicle that is supplied with oxygen a from an oxygen liquid storage tank I and with a hydrocarbon b from a tank II, electric energy and heat are obtained together with a by-product exhaust gas c as a result of the reaction of hydrocarbon with oxygen, said exhaust gas consisting, aside from water, mainly of carbonic acid. Said exhaust gas is dissolved in water in the device IV and then released out of the vehicle in accordance with the method according to claim 1.

[0016] For this purpose, sea water is made to flow through a pipe length 2 from inlet A to outlet B by means of a pump 4 or by the moving vehicle. Suitable flow velocities range between 1 and 3 m/s. Immersion pressure prevails at the inlet and at the outlet port. The exhaust gas C is discharged at a pressure below immersion pressure through a porous body 1 arranged inside of said pipeline. Sufficient pressure is thereby achieved by way of an appropriate method in the energy converter III or of a compressor in the exhaust gas stream c.

[0017] The quantity of sea water is determined in such a manner that the water is capable of completely dissolving the exhaust gas on account of its solvent power for gases. The quantity of water needed thereby depends on the composition of the exhaust gas, the temperature of the water and the immersion pressure.

[0018] In using static mixers 3 in pipe 2, the bubbles forming from the gas C are very small (<3 mm) and are prevented from combining into greater bubbles by the high turbulence generated by means of the mixers. The high turbulence and a sufficient length of the pipe of about 30 m for example cause the bubbles inside the pipe to completely dissolve. Accordingly, gas that might be located no longer exits site B. 

1. A method for discharging signature free exhaust gas from underwater vehicles, said exhaust gas being a by-product of the production of electric energy in energy converters, wherein said exhaust gas is directed by means of pressure into at least one pipe length (2) that is supplied, between an inlet (A) and an outlet (B), with outboard water (sea water) by way of a pump (4), the thereby generated gas bubbles being reduced by means of static mixers (3) arranged inside of the pipe length (2) through which water is flowing, with the gas being dissolved by the high turbulence of the fluid.
 2. The method of claim 1, wherein the exhaust gas is introduced into the pipe length (2) by way of a porous body (1).
 3. The method of one of the previous claims, wherein the pipe length (2) is supplied with outboard water (sea water) by the moving underwater vehicle, immersion pressure prevailing between the points A and B.
 4. The method of one of the previous claims, wherein the flow velocity of the water inside the pipe length (2) amounts to 1-3 m/s.
 5. The method of one of the previous claims, wherein the exhaust gas is introduced into the pipe length (2) at a pressure above the immersion pressure.
 6. A device for discharging signature free exhaust gas from underwater vehicles, said exhaust gas being a by-product of the production of electric energy in energy converters, wherein at least one pipe length (2) is arranged in the underwater vehicle, said pipe length being provided with an inlet (A) for outboard water (sea water), an outlet (B) for the exhaust gas dissolved in the water, and an injection site (1) for the exhaust gas to be introduced into the pipe length (2), at least one static mixer (3) being provided inside of said pipe length.
 7. The device of claim 6, wherein a pump (4) is arranged in the region A of the pipe length (2).
 8. The device of one of the previous claims, wherein the injection site (1) consists of a quadrant pipe with an injection lance and a porous body.
 9. The device of one of the previous claims, wherein the length of the pipe (2) is such that it allows complete dissolution of the gas bubbles of the exhaust. 